Change 'ROS2' to 'ROS 2' in README (#2235)

Signed-off-by: Christophe Bedard <[email protected]>
(cherry picked from commit 3ec9086)

Author: christophebedard

README.md

@@ -311,7 +311,7 @@ output_bags:
 
 When starting a recording or playback, you can pass a YAML file that contains QoS profile settings for a specific topic.
 The YAML schema for the profile overrides is a dictionary of topic names with key/value pairs for each QoS policy.
-Below is an example profile set to the default ROS2 QoS settings.
+Below is an example profile set to the default ROS 2 QoS settings.
 
 ```yaml
 /topic_name: